On October 3, 1996, Richard DiGuglielmo stopped by his family’s deli in Dobb’s Ferry to help his father, who was recovering from a heart attack, with the pre-dinner rush. Due to tenants’ complaints about the lack of parking, Richard Sr., was protective of the small lot in front. So when Charles Campbell pulled into a spot reserved for “patrons only,” DiGuglielmo Sr. asked him to move to a nearby lot. Campbell refused. A fight ensued. DiGuglielmo says he tried to save his father’s life, but what happened next changed his life forever.

Deborah Feyerick examines the case against a former NYC transit officer who is sitting in prison - maybe for life - even after the trial that put him there was found by a judge to be full of holes. It is a story of anger, and a death that started over a parking space.

Was it murder or a miscarriage of justice?

Twisted Justice is one of two revealing investigations you won’t want to miss on CNN Presents this Saturday at 8:00 pm ET, reairing at 11:00 pm and 2:00 am.

The moment 18-year-old Army Private Tim Josephs arrived at Edgewood Arsenal in 1968, he knew there was something different about the place.

“It just did not look like a military base, more like a hospital,” recalled Josephs, a Pittsburgh native. Josephs had volunteered for a two-month assignment at Edgewood, in Maryland, lured by three-day weekends closer to home.

“It was like a plum assignment,” Josephs said. “The idea was they would test new Army field jackets, clothing, weapons and things of that nature, but no mention of drugs or chemicals.”

But from 1955 to 1975, military researchers at Edgewood were using Army volunteers to test chemicals ranging from potentially lethal nerve gases like VX and sarin to incapacitating agents like BZ. The military also tested tear gas, barbiturates, tranquilizers, narcotics and hallucinogens like LSD.

This top secret Cold War research program initially looked for ways to defend against a chemical or biological attack by the Soviet Union, thought to be far ahead of the United States in “psycho-chemical” warfare. But the research expanded into offensive chemical weapons including one that could, according to one Army film obtained by CNN, deliver a “veritable chemical ambush” against an enemy.

Join CNN's Dr. Sanjay Gupta for more from his investigative report on U.S. soldiers used as drug test subjects. CNN Presents premieres Sunday at 8pm ET, re-airing at 11pm and 2am ET.